This invention concerns a process for drying materials. More particularly, it concerns a process for drying solid, moist carbonaceous materials at a relatively low temperature. The utility of the invention lies in its application to the drying of run-of-mine carbonaceous material, such as lignite, preparatory to the gasification of the lignite.
The drying of solid carbonaceous materials, before further processing, is well known. By reducing the moisture level of these materials, the calorific value per unit wt. is enhanced. Many materials, such as coal and mineral ores, are conventionally dried by countercurrent treatment with hot combustion gases. Another method of dehydrating lignite is described in U.S. Pat. No. 2,610,115, in which ground lignite is mixed with a mineral hydrocarbon oil and the mixture is heated to a temperature of 350.degree. F., during which process moisture is removed from the lignite and hydrocarbon vapors are adsorbed within the lignite mass. Another method of drying a wetted material is found in U.S. Pat. No. 3,982,325, in which a solvent medium bath comprising a mixed solvent system having a plurality of layers contacts the wetted material and removes moisture from the wetted material. The wetted solvent is then subjected to azeotropic distillation which regenerates the solvent medium.